1. Technical Field of the Invention
The present invention relates generally to the detection of ultrasonic waves and more particularly to a capacitive detection apparatus and method for detecting acoustic waves in a sample.
2. Discussion of the Related Art
The detection of ultrasonic waves is important in a wide variety of applications including materials characterization and medical analysis. Current transducers fall into two broad categories of piezoelectric elements or magnetic concepts, Well-damped piezoelectric transducer elements are normally designed to operate from 100-250 KHz up to 250 MHz, Specifically shaped piezoelectric elements designed for point contact use low frequency responses from 50 KHz to approximately 2 MHz. Both types of transducers are not true specimen displacement sensors since the voltage generated is a result of compression of the transducer by the ultrasonic waves. In addition, these transducers acoustically interact with the ultrasonic wave, thereby altering the detected wave.
The magnetic units employ eddy currents and magnetic fields to detect both bulk waves and surface waves. A strong, homogeneous magnetic field is required to measure absolute amplitudes. Both sufficient strength and homogeneity are difficult to maintain.